Abstract

The synthesis of proteins has been analyzed in young seedlings of a winter and a spring variety of rapeseed (Brassica napus) at two different temperatures, 18°C and 0°C. The different polypeptides were separated by two dimensional polyacrylamide gel electrophoresis. The synthesis of several polypeptides is stimulated at 0°C whereas that of others is repressed. Similar changes in the mRN A population are also obvious when mRNAs obtained from coldtreated and control seedlings are translated in vitro in a cell-free system and then the translation products are compared. Several mRNAs are apparently more abundant at 0°C than at 18°C while others are less abundant or have completely disappeared. Differences were noticed in the response of the winter and spring varieties at the low temperatures. L-phenylalanine ammonia-lyase is induced specifically in the cold-tolerant cultivar, suggesting that it might be a useful biochemical marker in predicting the cold sensitivity of new variety or in improving a sensitive cultivar.